At the heart of the dispute between two modern-day kingdoms is a 10th century Hindu temple devoted to Shiva. Preah Vihear is in Cambodia – thanks to a 1962 verdict by the International Court of Justice (ICJ) – but the traditional and the easiest way to access it is through the northern entrance, which lies in Thailand. The Thais, who never fully reconciled to the ICJ’s verdict, were enraged in 2008 when another international institution, the United Nations Educational, Scientific and Cultural Organisation (UNESCO), sought to designate Preah Vihear as a World Heritage Site. The two countries have engaged in a number of armed skirmishes since then, with a 460-hectare tract of disputed land in the vicinity of the temple being the focus of the conflict.

The dispute has come in handy for the various actors engaged in the extended political drama in Thailand. A few weeks ago, Thai politicians “inspecting” the border regions were arrested by Cambodian authorities for illegally entering Cambodia, sparking off a new wave of armed conflict. The two countries exchanged artillery fire and Thai Prime Minister Abhisit Vejjajiva despatched tanks to the border. Meanwhile, Hun Sen, Cambodia’s battle-hardened prime minister, appointed his own son, a recently promoted major-general, to lead the forces defending Preah Vihear. He also called for the UN Security Council (UNSC) to intervene, a move that Thailand promptly rejected. The UNSC, as usual, lamely called for “maximum restraint”, “permanent ceasefire”, “effective dialogue” and passed the buck to the Association of Southeast Asian Nations (Asean).

Yet, Asean, a regional grouping often celebrated for its pragmatism and competence, has been unable to keep two of its members from going to war with each other. It will now try to play peacemaker, but it is unlikely that it can achieve anything beyond temporary damage control. Cambodia has legal title, but Thailand is more powerful. Preah Vihear is intertwined with Thailand’s domestic political turmoil, and because Asean cannot interfere in the internal affairs of its members, meaningful mediation will have to wait until the unrest, intrigue and ferment in Bangkok subsides. Even then, there is no guarantee that the Thais will allow their relative power advantage to be neutralised by accepting third-party arbitration.

Asean’s failure to prevent the Thai-Cambodian border dispute from escalating into a shooting war calls into question its ability to take on the more challenging project of anchoring East Asia’s security architecture. That’s not all. Asean states have been extremely reluctant to maintain solidarity with their counterparts in the latter’s disputes with non-Asean states. It is to the US that Vietnam and the Philippines turned last year when China upped the ante over the maritime territorial disputes in the South China Sea.

But Laos, Cambodia, Thailand and Vietnam – lower riparians of the Mekong river – have no one to turn to in the dispute over water sharing with China. Beijing refuses to be part of the Mekong River Commission framework. It has observer status but does not fully share hydrological information on each of the dams it is building, creating anxiety in the downstream countries where a vast numbers of people rely on the river for their livelihood. According to Ame Trandem, a campaigner with International Rivers, an NGO, “Environmentalists in the region have continuously requested regional leaders to bring the issue of the Mekong dams to the Asean platform.” Countries such as Indonesia, Singapore and the Philippines, she adds, “should publicly call for the Mekong River to remain free-flowing and healthy, while assisting fellow Asean countries to study less destructive and more sustainable energy options”.

But getting China to cooperate over managing the Mekong river waters requires more than that. Timo Menniken, a German scholar, argues, “Efforts have to concentrate on constructing a balance of power than appealing to China’s altruism.” He calls for Asean to adopt a common foreign policy over the Mekong, bolster Cambodia, Laos, Vietnam and Thailand with economic assistance and take up the issue with China at Asean-centred regional security fora. Driving a grand bargain with China, by “offering incentives in non-water fields in return for cooperative management of shared water resources” requires Asean to demonstrate solidarity that has hitherto been lacking. The Asean Foundation’s Makarim Wibisono recently lamented that the “‘we feeling’ is still absent in the minds of Asean people”.

As South East Asian countries become increasingly dependent on China, Beijing will succeed in co-opting Myanmar, Laos, Thailand and, perhaps, even Cambodia into joining its bandwagon. You can see why suspicions, disputes and conflicts among these countries will not be perceived as an undesirable state of affairs by China.

From Preah Vihear to the Mekong basin, from Myanmar to the South China Sea, the list of regional security issues where Asean is falling short is growing. It is likely that the business of providing a robust security architecture for the region will, as before, fall to non-members — this time the US, China and India.

The author is founder and fellow for geopolitics at the Takshashila Institution and editor of Pragati — The Indian National Interest Review